This type of vehicle power system in the conventional art supplies power to individual ECUs (electronic control units) from at least either one of a generator and a battery, as disclosed in JP-A-2003-003889, via a protective function, such as a fuse or a fusible link, and a power-distribution function, such as a relay. Each of the ECUs is provided therein with a power circuit to individually generate a power-supply voltage required in the ECU.
However, being provided with a power circuit in each of the ECUs, the size of individual ECUs is unavoidably increased in the above vehicle power system of the conventional art. Thus, the vehicle power system of the conventional art has suffered from a problem of requiring a large space for arranging the ECUs.